The medicine, Daraprim, which has been on the market for 62 years, is the standard of care for a food-borne illness called toxoplasmosis caused by a parasite that can severely affect those with compromised immune systems. Turing purchased the rights to the drug last month and almost immediately raised prices.

Alarmed consumers took to Reddit to call for a boycott of the company's products (with some pointing out that it's hard to boycott a drug if you'll die without it) and calling for new laws to prevent this kind of thing from happening in the future.

Judith Aberg, a spokesperson for the HIV Medicine Association, has calculated that even patients with insurance could wind up paying $150 per pill out of pocket. "This is a tremendous increase," she told USA Today.

The New York Times reported that Alberg's group and the Infectious Diseases Society of America wrote in a joint letter to Turing earlier this month complaining that the price increase is "unjustifiable for the medically vulnerable patient population" and "unsustainable for the health care system."

The news even got the attention of Democratic presidential candidate Hillary Rodham Clinton, who called the pricing "outrageous" and promised that she had a plan to take on the issue. Clinton is scheduled to unveil a highly anticipated drug pricing proposal today.

The tweet drew strong reaction from Wall Street, sending the Nasdaq biotech index down 4.41 per cent on Monday.

Presidential hopeful Bernie Sanders, an independent senator from Vermont, and Representative Elijah E Cummings (D-Md.) drew Turing into an already ongoing congressional investigation into recent drug price increases, sending a letter on Monday asking for information about total gross revenues from sales of Daraprim; prices paid for all sales; the prices in foreign markets; and the identity of company official(s) responsible for setting the price.

"The enormous, overnight price increase for Daraprim is just the latest in a long list of skyrocketing price increases for certain critical medications," Sanders and Cummings said. "Americans should not have to live in fear that they will die or go bankrupt because they cannot afford to take the life-saving medication they need."

Turing spokesman Craig Rothenberg has said the company will use the money from the sales to further research treatments for toxoplasmosis, which he said has long been neglected. He also said the firm had plans to invest in marketing and education tools to raise awareness of the disease — a reasonable and reasoned answer, but one that has been unsatisfactory for many.

(In an interview with The Washington Post on Monday, the company said the pill is actually $18 a tablet so the price increase is 4,100 per cent. Media outlets had previously reported that the jump was more than 5,000 per cent if based on an original price of $13.50.)

John Carroll, the editor of Fierce Biotech, a daily newsletter about the industry, was one of the first to ask Turing chief executive Martin Shkreli directly to explain the move. In a hot-headed Twitter exchange over the weekend, Shkreli declined to provide additional information and instead launched into a series of personal attacks against Carroll — calling him "irrelevant" and someone who doesn't "think logically".